BBC time pips (thing)

Since 1924 the BBC have used a time signal of six short pips to mark the hour. They begin at the 55-second instant, and the new minute begins at the beginning of the sixth pip, which is somewhat longer.

Not every hour: on the music station Radio 3 they only use them when they are about to have a short news bulletin, so that's mainly in the morning, and the main news on Radio 4 is introduced by the powerful chimes of Big Ben. But the "pips" as they are called, officially the "Time Signal", are very distinctive and instantly recognized.

When a leap second is added to a day to bring UTC (formerly called Greenwich Mean Time) into line with the earth's orbit, a seventh pip is used: the six short ones are at seconds 55 to 60, and the longer one still begins the new minute, at second 61 (= 00).

More detail at:http://news.bbc.co.uk/hi/english/sci/tech/newsid_271000/271319.stm
which is a news story from February 1999, when the Dent clocks were taken out of retirement and displayed at Greenwich for the 75th anniversary of the pips.